3D Nonvolatile Memory Preprogramming for Over-Erased Cell Retention
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Solution Overview
Problem
Nonvolatile memory devices with three-dimensional structures face increased interference or disturbance between memory cells, leading to degraded retention characteristics due to over-erased memory cells.
Innovation Solution
A preprogram operation is performed to increase the threshold voltages of over-erased memory cells before data programming, followed by a data program operation, reducing disturbance and enhancing retention characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If three-dimensional structures are used to increase device integration and memory capacity, then memory capacity and integration degree are improved, but interference between memory cells increases and retention characteristics are degraded
Solution Approach 1:
The patent applies preliminary action by performing a preprogram operation before the main data program operation. This preprogram operation proactively increases the threshold voltages of over-erased memory cells to a level that prevents future interference issues, thereby maintaining retention characteristics even in high-density three-dimensional structures.
Solution Approach 2:
The patent implements preliminary anti-action by counteracting the potential harmful effect of over-erased cells before they can cause interference. By detecting and pre-programming over-erased cells in advance, the system prevents the degradation of retention characteristics that would otherwise occur in high-capacity three-dimensional memory structures.
2Reliability
If a preprogram operation is performed on over-erased memory cells, then retention characteristics are improved, but operation complexity increases
Solution Approach 1:
The patent applies local quality by performing the preprogram operation only on specific over-erased memory cells that are identified as needing intervention, rather than uniformly processing all memory cells. This targeted approach improves retention characteristics while minimizing the additional operation complexity to only the necessary subset of cells.
Solution Approach 2:
The patent implements feedback by using the write address to determine which memory cells are over-erased and require preprogramming. This feedback mechanism allows the system to intelligently identify and treat only the problematic cells, reducing overall operation complexity while maintaining improved retention characteristics.
3Object-affected harmful factors
If preprogram operation is performed before data program operation, then memory cell interference is reduced, but operation time increases
Solution Approach 1:
The patent applies partial action by performing the preprogram operation only on the subset of memory cells that are over-erased and identified through the write address, rather than uniformly processing all memory cells. This reduces the additional time required while still effectively reducing memory cell interference in the problematic areas.
Solution Approach 2:
The patent implements preliminary action by performing the preprogram operation during the data transfer phase, before the main data program operation begins. This timing strategy allows interference reduction to occur in advance, and the operations are overlapped efficiently to minimize the total time impact.
Data Source
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AI summary
A method of controlling a nonvolatile memory device, includes: determining, based on a write address, whether selected memory cells of the nonvolatile memory device corresponding to the write address are included in an over-erased group; based on the selected memory cells being included in the over-erased group, performing a preprogram operation to increase threshold voltages of an over-erased state of the selected memory cells; and after completion of the preprogram operation, performing a data program operation to store write data in the selected memory cells.